1/06/2008

The bike in question currently wears 700x23 Hutchinson Excel tires which measure around 24mm wide on Open Pro rims. Although the frame and fork have clearance for perhaps 30-32mm rubber, that width is constrained by the max opening of the RX100 brake calipers using the integral quick-releases AND screwing down the brake-cable barrel adjusters: 28mm. (A Tangent: I wish somebody would produce an inline cable quick-release mechanism for these situations! Problem Solvers, are you listening?!?)

In response to my quest, a very kind iBOB list-member contacted me, expressing his desire to divest his garage of an overgrown stash of bike parts and tires, indicating that he had a couple pairs of tires in that size range that he'd gladly send my way, gratis. I was overjoyed! The tires arrived about a week later, and I marveled at the fact that they were near-new with no detectable wear! I was sent a set of 700x28 wire-bead Continental Sport 1000s and a set of 700x26 folding Panaracer Stradius Elite tires.

Last night, in anticipation of a break in the pouring rain we've been having and a chance to maybe get out for a ride, I test-mounted these tires. Here's the results:

> For those of us who would not understand the implications of a 40mm vs> 64mm trail fork for a Bleriot (me included), what does the lower trail> do to the handling of the bike. I have a Bleriot on order and the idea> of having a fork option is intriguing yet it is not obvious to me why I> would want the option.>> Apologies in advance if I am asking something that is obvious.>> Cheers,>> Mark>

It's not obvious at all, Mark. In fact, the whole trail thing is a bit ofa conceptual can of worms. Simply put, increasing trail (by decreasing thehead angle and/or reducing the fork offset) increases the front wheel'stendency to resist changes in direction and to recenter itself after asteering deviation, so high-trail bikes have more straight-line stability,in theory.

But that's not all there is to it. Increasing trail also increases the"wheel flop factor" -- the amount by which the front end of the bike lowersunder steering. If you put a bike in a workstand with the wheels justtouching the ground and turn the handlebars, you can see the front wheellift off the ground. The higher the trail, the higher the wheel will liftfor a given steering angle. This means that when you steer while ridingthe bike, a higher-trail bike will drop more at the front, and this willbegin to initiate a turn. So, in this sense, high-trail bikes are LESSstable, since it takes a smaller steering input to initiate a turn.

How do these factors combine in practice? I have some first-handexperience with this. A few months ago, Matthew sent me a spare fork formy Kogswell P62, and I had a local framebuilder increase its offset from45mm to 55mm. Compared to the original fork, the extra offset reduced theP's trail from ~59mm to ~48mm, which is lower than virtually all modernproduction bikes. (It also caused the head angle to increase by ~0.5° to73.5°, which is a confounding factor, but the main effect of that changewill be to reduce the bike's turn radius for any given steering angle.)

Compared to the original configuration, I've noticed the following effectsof changing to a lower-trail geometry:

- Lighter-feeling handling. There's noticeably less effort required toturn the bars. You might think that would make the low-trail bike twitchy,but that's not the case at all, since there's also less responsiveness tosteering inputs.

- Less tendency to veer. With higher trail, the bike would tend to veerunder careless or accidental steering inputs (shoulder-checking, reachingfor a water bottle, hitting an unseen bump, ...), since the high-trailgeometry is eager to initiate turns.

- Easier to change line in a turn. Some people like this, others preferthe high-trail tendency to stick to a single line throughout. Since I'mnot a great cornerer, I welcome the opportunity to change my mind in themiddle.

- More precise steering. Because the lower-trail bike doesn't want toinitiate a turn with each nudge of the handlebars, I find it easier to pickmy way through and around roadside debris.

In more general terms, the lower-trail geometry gives up nothing instability or confidence, while providing several advantages. I do like ita lot better.

You may also be interested in some results of testing the Kogswell P/Rprototype with three different fork offsets.http://kogswell.com/testPR.pdf

trying stuff out for yourself -- instead of merely relying on and believing equipment reports/reviews that I read about online and in print, I've made it a priority to educate myself by personally trying a few of these things out (eg., 650B wheels, low-trail geometry)